Electric Machines with Energizable and Non-Energizerable U-Shaped Stator Segments

ABSTRACT

A method of making a stator module for use in a stator assembly of an electric machine includes temporarily supporting a plurality of stator segments in a desired orientation using a temporary support. The desired orientation of the stator segments is a relative orientation of the stator segments within the stator module. A mold is placed around the plurality of stator segments and the mold is filled with a potting material to form a stator module such that the potting material supports the stator segments in their desired orientation. The temporary support is removed.

BACKGROUND

The electric motor and/or generator industry is continuously searchingfor cost effective electric motors and/or generators with increasedefficiency and power density. For some time now, it has been believedthat motors and generators constructed using permanent super magnetrotors (for example cobalt rare earth magnets and Neodymium-Iron-Boronmagnets) and stators including electromagnets with magnetic cores formedfrom thin film soft magnetic material have the potential to providesubstantially higher efficiencies and power densities compared toconventional motors and generators. However, to date it has proved verydifficult to provide a cost effective and easily manufacturable motor orgenerator that includes magnetic cores formed from thin film softmagnetic materials.

Thin film soft magnetic low loss materials such as amorphous metal ornano-crystalline material are normally supplied in a thin continuoustape having a uniform tape width. Many other magnetic materials may alsobe provided in the form of a long continuous tape. For purposes of thisdescription, the term tape wound magnetic cores is meant to include anymagnetic core formed by winding a thin tape magnetic material into acoil to form a magnetic core.

SUMMARY

In general, aspects of the present disclosure are directed to methods ofmaking an electric motor and/or generator including a stator assemblyhaving a plurality of independently energizable stator segments witheach stator segment including an associated tape wound magnetic core.Aspects of the present disclosure also relate to methods of making anelectric motor and/or generator including a cast rotor. Aspects of thepresent disclosure further provide methods and arrangements forincreasing the efficiency and cost effectiveness of electric motorsand/or generators that use tape wound magnetic cores, as well as methodsfor manufacturing components for these electric motors and/orgenerators.

In some aspects, the present disclosure provides a rotating electricmachine including a rotor assembly supported for rotation about arotational axis and a stator assembly. The rotor assembly may include aplurality of rotor poles with the rotor poles supported for rotationalong a rotor pole circular path about the rotational axis with adesired rotor pole spacing between adjacent rotor poles. The statorassembly may include a plurality of independently energizable statorsegments with each stator segment including a magnetic core that definesa plurality of stator poles for magnetically interacting with the rotorpoles. The stator segments may be positioned adjacent to the rotor polecircular path such that the stator poles face the rotor pole circularpath with a desired stator pole spacing between adjacent stator poles.The stator segments may also be positioned adjacent to only a portion ofthe rotor pole circular path such that there is at least one stator polegap between at least two stator poles that is greater than the desiredstator pole spacing. The stator assembly may further include at leastone non-energizable termination magnetic core positioned within thestator pole gap and adjacent to one of the stator segments such that thetermination core provides an additional magnetic flux return path formagnetic flux associated with the energizing of the adjacent statorsegment.

In some aspects, the stator assembly may include a plurality ofindependent stator modules with each stator module including a pluralityof the stator segments and at least one of the independent statormodules including at least one termination magnetic core.

In some aspects, there may be a stator pole gap between each statormodule and each stator module may include at least one termination core.

In some aspects, the magnetic cores of the stator segments may beU-shaped magnetic tape wound cores formed from multiple layers of thinfilm soft magnetic tape material having a desired tape width and tapethickness. The two legs of each U-shaped magnetic tape wound core maydefine two stator poles of the associated stator segment.

In some aspects, the termination magnetic cores may be U-shaped magnetictape wound cores formed from multiple layers of thin film soft magnetictape material having a desired tape width and tape thickness.

In some aspects, the rotating electric machine may be a radial gapelectric machine and each stator segment may be positioned such that thetwo stator poles of each stator segment are located adjacent to oneanother and in line with one another along a line that is parallel withthe rotational axis of the electric machine. The rotor poles may bepairs of rotor poles formed from adjacent pairs of permanent magnetsegments configured to form rotor poles of opposite magnetic polarity.Each pair of permanent magnet segments may be positioned with the twopermanent magnet segments located adjacent to one another and in linewith one another along a line that is parallel with the rotational axisof the electric machine. The two permanent magnet segments may definetwo adjacent circular paths around the rotational axis of the electricmachine when the rotor is rotated about the rotational axis of theelectric machine. Each of the two adjacent circular paths may face anassociated one of the stator poles of each independently energizablestator segment.

In some aspects, the present disclosure provides a method of making arotating electric machine. The method may include providing a rotorassembly supported for rotation about a rotational axis. The rotorassembly may include a plurality of rotor poles with the rotor polesbeing supported for rotation along a rotor pole circular path about therotational axis with a desired rotor pole spacing between adjacent rotorpoles. The method may further include placing a stator assembly havingmultiple independently energizable stator segments adjacent to the rotorassembly. Each stator segment may include a magnetic core that defines aplurality of stator poles for magnetically interacting with the rotorpoles. The stator segments may be positioned adjacent to the rotor polecircular path such that the stator poles face the rotor pole circularpath with a desired stator pole spacing between adjacent stator poles.The stator segments may also be positioned adjacent to only a portion ofthe rotor pole circular path such that there is at least one stator polegap between at least two stator poles that is greater than the desiredstator pole spacing. At least one termination magnetic core may beplaced within the stator pole gap and adjacent to one of the statorsegments such that the termination core provides an additional magneticflux return path for magnetic flux associated with the energizing of theadjacent stator segment.

In some aspects, the stator assembly may include a plurality ofindependent stator modules with each stator module including a pluralityof the stator segments and the step of placing at least one terminationmagnetic core within the stator pole gap may include the step of placingat least one termination magnetic core in at least one of theindependent stator modules.

In some aspects, there may be a stator pole gap between each statormodule and each stator module may include at least one termination core.

In some aspects, the magnetic cores of the stator segments may beU-shaped magnetic tape wound cores formed by winding multiple layers ofthin film soft magnetic tape material having a desired tape width andtape thickness into an oval shape and cutting the winding into twoU-shaped pieces. The two legs of each U-shaped magnetic tape wound coremay define two stator poles of the associated stator segment.

In some aspects, the termination magnetic cores may be U-shaped magnetictape wound cores formed by winding multiple layers of thin film softmagnetic tape material having a desired tape width and tape thicknessinto an oval shape and cutting the winding into two U-shaped pieces.

In some aspects, the rotating electric machine may be a radial gapelectric machine and each stator segment may be positioned such that thetwo stator poles of each stator segment are located adjacent to oneanother and in line with one another along a line that is parallel withthe rotational axis of the electric machine. The rotor poles may bepairs of rotor poles formed from adjacent pairs of permanent magnetsegments configured to form rotor poles of opposite magnetic polarity.Each pair of permanent magnet segments may be positioned with the twopermanent magnet segments located adjacent to one another and in linewith one another along a line that is parallel with the rotational axisof the electric machine. The two permanent magnet segments may definetwo adjacent circular paths around the rotational axis of the electricmachine when the rotor is rotated about the rotational axis of theelectric machine. Each of the two adjacent circular paths may face anassociated one of the stator poles of each independently energizablestator segment.

In some aspects, the present disclosure provides a magnetic core for usein a stator assembly of an electric machine having a rotor with aplurality of rotor poles. The magnetic core may include a tape woundmagnetic core piece formed from multiple layers of thin film softmagnetic tape material of a desired tape width and tape thickness. Thetape wound magnetic core may define at least portions of a plurality ofstator poles adapted to magnetically interacting with the rotor poles ofthe electric machine. Each stator pole may haves a pole face adapted toface the rotor of the electric machine and each stator pole face mayinclude at least portions of the ends of at least some of the multiplelayers of thin film soft magnetic tape material. The magnetic core mayalso include a stator pole face enlarging piece attached to the statorpole portions of the tape wound magnetic core piece to enlarge thesurface area of the stator pole face and allow at least portions of theends of at least some of the multiple layers of thin film soft magnetictape material to form portions of the stator pole face.

In some aspects, the tape wound magnetic core piece may be a U-shapedmagnetic core piece formed by winding multiple layers of the thin filmsoft magnetic tape material into an oval shape and cutting the windingto form two U-shaped magnetic core pieces. Each U-shaped magnetic corepiece may define at least portions of two stator poles.

In some aspects, the stator pole face may include the cut ends of eachlayer of the thin film soft magnetic tape material.

In some aspects, the stator pole face enlarging piece may fully surroundthe stator pole portions of the tape wound magnetic core piece.

In some aspects, the stator pole face enlarging piece may be made from apressed powder magnetic material.

In some aspects, the stator pole face enlarging piece may have a uniformthickness perpendicular to the stator pole face.

In some aspects, the present disclosure provides a method of making amagnetic core for use in a stator assembly of an electric machine havinga rotor with a plurality of rotor poles. The method may include windingmultiple layers of a thin film soft magnetic tape material of a desiredtape width and tape thickness into a desired shape. The winding may becut to form a tape wound magnetic core piece that defines at leastportions of a plurality of stator poles adapted to magneticallyinteracting with the rotor poles of the electric machine. Each statorpole may have a pole face adapted to face the rotor of the electricmachine and each pole face may include at least portions of the cut endsof at least some of the multiple layers of thin film soft magnetic tapematerial. A stator pole face enlarging piece may be attached to thestator pole portions of the tape wound magnetic core piece to enlargethe surface area of the stator pole face and allow at least portions ofthe ends of at least some of the multiple layers of thin film softmagnetic tape material to form portions of the stator pole face.

In some aspects, the tape wound magnetic core piece may be a U-shapedmagnetic core piece formed by winding multiple layers of the thin filmsoft magnetic tape material into an oval shape and cutting the windingto form two U-shaped magnetic core pieces. Each U-shaped magnetic corepiece may define at least portions of two stator poles.

In some aspects, the stator pole face may include the cut ends of eachlayer of the thin film soft magnetic tape material.

In some aspects, the stator pole face enlarging piece may fully surroundthe stator pole portions of the tape wound magnetic core piece.

In some aspects, the stator pole face enlarging piece may be pressedfrom pressed powder magnetic material.

In some aspects, the stator pole face enlarging piece may have a uniformthickness perpendicular to the stator pole face.

In some aspects, the magnetic core may include electrically conductivewindings that are placed around the stator poles of the tape woundmagnetic core piece. The stator pole face enlarging piece may be adheredto the sides of the stator pole and adhered to at least portions of theelectrically conductive windings. This may assist in the structuralsupport of the stator pole face enlarging piece.

In some aspects, the present disclosure provides a method of making arotating electric machine having a rotational axis. The method mayinclude providing a stator assembly that defines a plurality of statorpoles positioned adjacent to at least portions of a rotor pole circularpath about the rotational axis of the electric machine. A rotor housingmay be cast from a desired casting material and a plurality of rotorpoles may be formed in the rotor housing to create a rotor assembly withthe rotor housing providing a magnetic flux return path for the rotorpoles. The rotor assembly may be supported for rotation about therotational axis of the electric machine such that the plurality of rotorpoles are supported for rotation along the rotor pole circular path.

In some aspects, the casting material may be a cast iron.

In some aspects, the cast iron may be grey iron.

In some aspects, the step of casting a rotor housing may include thestep of providing a magnetic back iron and casting a rotor housing froma desired casting material around the back iron.

In some aspects, the magnetic back iron may be an iron alloy band.

In some aspects, the desired casting material may be an aluminum alloycasting material.

In some aspects, the step of forming a plurality of rotor poles in therotor housing may include the step of supporting a plurality ofpermanent magnets in the rotor housing to form the rotor poles.

In some aspects, the step of supporting a plurality of permanent magnetsin the rotor housing may include the step of using a magnet spacingtrack to place the permanent magnets in desired locations in the rotorhousing and the step of adhering the permanent magnets and magnetspacing track to the rotor housing to form the rotor assembly.

In some aspects, the electric machine may be a radial gap machine.

In some aspects, the rotor poles may be pairs of rotor poles formed fromadjacent pairs of permanent magnet segments configured to form rotorpoles of opposite magnetic polarity. Each pair of permanent magnetsegments may be positioned such that the two permanent magnet segmentsare located adjacent to one another and in line with one another along aline that is parallel with the rotational axis of the electric machinesuch that the two permanent magnet segments define two adjacent circularpaths around the rotational axis of the electric machine when the rotoris rotated about the rotational axis of the electric machine.

In some aspects, the stator poles may face outward away from therotational axis and the rotor assembly may surround the stator assemblywith the rotor poles facing inward toward the rotational axis.

In some aspects, the electric machine may be a wheel hub motor.

In some aspects, the present disclosure provides a method of making arotor assembly for use in a rotating electric machine having arotational axis. The method may include casting a rotor housing from adesired casting material. A plurality of rotor poles may be formed inthe rotor housing to create a rotor assembly with the rotor housingproviding a magnetic flux return path for the rotor poles. The rotorassembly may be supported for rotation about the rotational axis of theelectric machine such that the plurality of rotor poles are supportedfor rotation along the rotor pole circular path.

In some aspects, the casting material may be a cast iron.

In some aspects, the cast iron may be grey iron.

In some aspects, the step of casting a rotor housing may include thestep of providing a magnetic back iron and casting a rotor housing froma desired casting material around the back iron.

In some aspects, the magnetic back iron may be an iron alloy band.

In some aspects, the desired casting material may be an aluminum alloycasting material.

In some aspects, the step of forming a plurality of rotor poles in therotor housing may include the step of supporting a plurality ofpermanent magnets in the rotor housing to form the rotor poles.

In some aspects, the step of supporting a plurality of permanent magnetsin the rotor housing may include the step of using a magnet spacingtrack to place the permanent magnets in desired locations in the rotorhousing and the step of adhering the permanent magnets and magnetspacing track to the rotor housing to form the rotor assembly.

In some aspects, the electric machine may be a radial gap machine.

In some aspects, the rotor poles may be pairs of rotor poles formed fromadjacent pairs of permanent magnet segments configured to form rotorpoles of opposite magnetic polarity. Each pair of permanent magnetsegments may be positioned such that the two permanent magnet segmentsare located adjacent to one another and in line with one another along aline that is parallel with the rotational axis of the electric machinesuch that the two permanent magnet segments define two adjacent circularpaths around the rotational axis of the electric machine when the rotoris rotated about the rotational axis of the electric machine.

In some aspects, the rotor poles may face inward toward the rotationalaxis.

In some aspects, the electric machine may be a wheel hub motor.

In some aspects, the present disclosure provides a rotating electricmachine having a rotational axis. The electric machine may include astator assembly that defines a plurality of stator poles positionedaround at least portions of a circular path about the rotational axis ofthe electric machine. A rotor assembly may be supported for rotationabout the rotational axis of the electric machine. The rotor assemblymay include a plurality of rotor poles that are supported for rotationalong a rotor pole circular path about the rotational axis of theelectric machine. The rotor assembly may also include a cast rotorhousing for supporting the plurality of rotor poles for rotation aboutthe rotational axis of the electric machine.

In some aspects, the present disclosure provides a rotor for use in arotating electric machine having a rotational axis. The rotor mayinclude a plurality of rotor poles that are supported for rotation alonga rotor pole circular path about the rotational axis of the electricmachine. The rotor may also include a cast rotor housing for supportingthe plurality of rotor poles for rotation about the rotational axis ofthe electric machine.

In some aspects, the present disclosure provides a method of making astator module for use in a stator assembly of an electric machine. Themethod may include temporarily supporting a plurality of stator segmentsin a desired orientation using a temporary support with the desiredorientation of the stator segments being a relative orientation of thestator segments within the stator module. A mold may be placed aroundthe plurality of stator segments and the mold may be filled with apotting material to form a stator module such that the potting materialsupports the stator segments in their desired orientation. The temporarysupport may be removed.

In some aspects, the temporary support may be a magnetic jig that usesmagnetic force to support the plurality of stator segments in thedesired orientation.

In some aspects, the magnetic jig may include a permanent magnetassociated with each stator segment with each permanent magnet providinga magnetic force that holds its associated stator segment against astator segment orienting surface.

In some aspects, the mold may be a stator module housing that remainspart of the stator module.

In some aspects, the potting material may be the only materialstructurally supporting the stator segments in their desired orientationwithin the stator module after the temporary support is removed.

In some aspects, the potting material may be a thermally conductiveepoxy and filler mixture.

In some aspects, the potting material may be a pourable powder mixtureincluding a heat activated powered adhesive and a filler.

In some aspects, the filler may be an alumina coated aluminum powder.

In some aspects, each stator segment may include at least oneelectrically conductive winding for independently energizing the statorsegment and each winding may include electrically conductive leads forelectrically connecting the electrically conductive windings to otherelectrical components. The method may further include the step ofelectrically interconnecting the electrically conductive leads of theelectrically conductive windings using an electrical connectionarrangement. The step of placing a mold around the plurality of statorsegments may include the step of placing the mold around the electricalconnection arrangement. The step of filling the mold with a pottingmaterial to form a stator module may include the step of filling themold with a potting material to form a stator module with the pottingmaterial supporting the stator segments and electrical connectionarrangement within the stator module.

In some aspects, the electrical connection arrangement may be a printedcircuit board.

In some aspects, the printed circuit board may include a controller forcontrolling the operation of the individually energizable statorsegments.

In some aspects, the method may include using a plurality of differentelectrical connection arrangements to provide a plurality of differentstator module electrical configurations without varying other componentsmaking up the stator module.

In some aspects, the plurality of stator module electricalconfigurations may include different electric machine operatingvoltages.

In some aspects, the present disclosure provides a method of making arotating electric machine having a rotational axis. The method mayinclude providing a plurality of stator modules with each stator moduledefining a plurality of stator poles. A stator module supportarrangement may be provided for supporting the stator modules. A statormodule positioning jig may be used to position the stator modules in adesired location on the stator module support arrangement such that thestator poles of the stator modules are positioned adjacent to at leastportions of a rotor pole circular path about the rotational axis of theelectric machine. The stator modules may be attached to the statormodule support arrangement such that the stator modules are fixed in thedesired location on the stator module support arrangement. A rotorassembly having a plurality of rotor poles may be provided and the rotorassembly may be attached to the stator module support arrangement forrotation about the rotational axis of the electric machine such that theplurality of rotor poles are supported for rotation along the rotor polecircular path.

In some aspects, the stator module support arrangement may includeindexing features for holding the stator modules in the desired locationonce the stator modules have been attached to the stator module supportarrangement.

In some aspects, the indexing features may include a position lockingsurface finish on the contact surfaces between the stator modules andthe stator module support arrangement.

In some aspects, the position locking surface finish may be a knurledsurface finish.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic illustration of an electric machine includingstator modules and stator segments in accordance with aspects of thepresent disclosure.

FIG. 2 is a cross sectional view of the electric machine of FIG. 1illustrating a stator segment and a stator module housing in accordancewith aspects of the present disclosure.

FIG. 3 is a perspective view of a stator segment of FIG. 1 in accordancewith aspects of the present disclosure.

FIG. 4 is a plan view of a winding used to provide a stator core inaccordance with aspects of the present disclosure.

FIG. 5 is a plan view of a stator core in accordance with aspects of thepresent disclosure.

FIG. 6 is a schematic illustration of an electric machine includingstator modules and stator segments in accordance with aspects of thepresent disclosure.

FIG. 7 is a perspective view of a termination core of FIG. 1 inaccordance with aspects of the present disclosure.

FIG. 8 is a perspective view of the rotor assembly of FIG. 1 inaccordance with aspects of the present disclosure.

FIG. 9 is a perspective view of a molding arrangement for molding therotor housing of the rotor assembly of FIG. 8 in accordance with aspectsof the present disclosure.

FIG. 10 is a schematic illustration of a stator module supportarrangement in accordance with aspects of the present disclosure.

FIG. 11 is a cross sectional view of a stator assembly and a positioningjig used to position and attach the stator modules to the stator modulesupport arrangement of FIG. 10 in accordance with aspects of the presentdisclosure.

FIG. 12 is a flow chart illustrating various steps that may be includedin the process of making a stator module in accordance with aspects ofthe present disclosure.

FIG. 13 is a perspective view of a temporary support arrangement for usein the process of making a stator module in accordance with aspects ofthe present disclosure.

FIG. 14 is a perspective view of the temporary support arrangement ofFIG. 13 with components placed on the temporary support arrangement inaccordance with aspects of the present disclosure.

FIG. 15 is a perspective view of the temporary support arrangement ofFIG. 14 with additional components placed on the temporary supportarrangement in accordance with aspects of the present disclosure.

FIG. 16 is a perspective view of a stator module constructed inaccordance with aspects of the present disclosure.

FIG. 17 is a schematic illustration of a first winding pattern andelectrical configuration for interconnecting the windings of an electricmachine in accordance with the present disclosure.

FIG. 18 is a schematic illustration of a second winding pattern andelectrical configuration for interconnecting the windings of an electricmachine in accordance with the present disclosure.

FIG. 19 is a schematic illustration of an electric machine includingstator modules and stator segments in accordance with aspects of thepresent disclosure.

Like reference numerals in the various drawings indicate like elements.

DETAILED DESCRIPTION

Aspects of the present disclosure are directed to methods of making anelectric motor and/or generator including a stator assembly having aplurality of independently energizable stator segments with each statorsegment including an associated tape wound magnetic core. Aspects of thepresent disclosure also relate to methods of making an electric motorand/or generator including a cast rotor. Aspects of the presentdisclosure further provide methods and arrangements for increasing theefficiency and cost effectiveness of electric motors and/or generatorsthat use tape wound magnetic cores, as well as methods for manufacturingcomponents for these electric motors and/or generators. U.S. Pat. Nos.6,603,237, 6,879,080, 7,030,534, and 7,358,639 and PCT patentapplications PCT/US2010/048019, PCT/US2010/048027, andPCT/US2010/048028, all of which are incorporated herein by reference intheir entireties for all purposes, are directed to certain electricmotors and/or generators that may include tape wound magnetic cores.

Referring now to FIG. 1, an electric machine 10 in accordance withaspects of the present disclosure is illustrated. Electric machine 10may include, but is not limited to, an electric motor and/or an electricgenerator. Electric machine 10 includes a rotor assembly 12, a statorassembly 14, a bus bar module 16, and a controller 18. Controller 18regulates operation of electric machine 10 based on an input signal 20and a position signal 22. Input signal 20 may include a throttle signal,for example, in the case where electric machine 10 is implemented in avehicle, motorcycle, scooter, or the like. The electric machine mayinclude a Hall Effect sensor or other position detecting arrangement 24for detecting the position of rotor assembly 12 relative to statorassembly 14. The Hall Effect sensor or other position detectingarrangement 24 may generate position signal 22 used by the controller.Controller 18 may regulate power provided to electric machine 10 from apower source 26, when electric machine 10 is operating in a motor mode.Electric machine 10 may generate power that can be provided to, andstored in power source 26, when electric machine 10 is operating in as agenerator.

Although electric machine 10 may be provided as a DC brushless motor, itis contemplated that electric machine 10 may be provided as one of avariety of other types of electric machines within the scope of thepresent disclosure. Such electric machines include, but are not limitedto, DC synchronous electric machines, variable reluctance or switchedreluctance electric machines, and induction type electric machines. Forexample, permanent magnets may be implemented as the rotor poles ofelectric machine 10, in the case where electric machine 10 is providedas a DC brushless electric machine, as discussed in further detailbelow. In the case of a switched reluctance electric machine, or aninduction electric machine, the rotor poles may be provided asprotrusions of other magnetic materials formed from laminations ofmaterials such as iron or preferably thin film soft magnetic materials,for example. In other arrangements, the rotor poles can be provided aselectromagnets.

In the arrangement of FIG. 1, electric machine 10 may be provided as ahub-type electric machine with rotor assembly 12 located around theouter perimeter of electric machine 10. That is, stator assembly 14 maybe surrounded by rotor assembly 12. Although not illustrated in FIG. 1,rotor assembly 12 may be supported by bearings to rotate relative tostator assembly 14. A radial gap 28 separates rotor assembly 12 fromstator assembly 14. In alternative arrangements, rotor assembly 12 maybe supported for rotation relative to stator assembly 14 about arotational axis 30 using other suitable means. Although electric machine10 is described as a radial gap machine with the stator assembly beingsurrounded by the rotor assembly, this is not a requirement. Instead,the machine may be a radial gap machine with the stator assemblysurrounding the rotor assembly. Alternatively, the rotor assembly andthe stator assembly may be axially adjacent to one another forming anaxial gap machine.

In the example of FIG. 1, rotor assembly 12 includes fifty-six pairs ofradially adjacent permanent magnets 32 that form the rotor poles ofrotor assembly 12. In some implementations, the pairs of permanentmagnets 32 may be provided as super magnets such as cobalt rare earthmagnets, or any other suitable or readily providable magnet material. Asillustrated best in the cross sectional view of FIG. 2, each of thepairs of permanent magnets 32 includes a first magnet oriented to form anorth rotor pole 32 a, and a second magnet oriented to form a southrotor pole 32 b. The first magnet is located adjacent to the secondmagnet such that the two permanent magnets are in line with one anotheralong a line that is generally parallel with the rotational axis 30 ofelectric machine 10. Accordingly, the two permanent magnets defineadjacent circular paths about the rotational axis 30 of electric machine10 when rotor assembly 12 rotates. As shown in FIG. 2, the permanentmagnet pairs are positioned around the inside periphery of rotorassembly 12 facing radial gap 28. Each consecutive pair of permanentmagnets 32 is reversed such that all of the adjacent magnet segmentsalternate from north to south around the entire rotor assembly 12.

Although permanent magnet pairs 32 may be provided as permanent supermagnets, other magnetic materials can be implemented. In some examples,electromagnets may be implemented with rotor assembly 12 in place ofpermanent magnets. In addition, although rotor assembly 12 of FIG. 1 isillustrated as including fifty-six magnet pairs, it is contemplated thatrotor assembly 12 may include any number of magnet pairs.

Stator assembly 14 includes a plurality of stator modules 40. In thearrangement of FIG. 1, stator assembly 14 includes six stator modules40, which are designated by reference numerals 40 a, 40 b, 40 c, 40 d,40 e and 40 f in FIG. 1 for descriptive purpose. Although statorassembly 14 is described as including six stator modules 40, otherarrangements are contemplated. For example, stator assemblies includingmore than six stator modules 40, or less than six stator modules 40 arewithin the scope of the present disclosure, as discussed in furtherdetail below.

Each stator module 40 of electric machine 10 is independent from theother stator modules 40 in stator assembly 14. More specifically, eachstator module 40 is independently removable and replaceable. In someimplementations, a stator module 40 may be removed, and electric machine10 can operate with less than a full complement of stator modules 40.Considering the specific arrangement of FIG. 1, for example, electricmachine 10 may operate with more or less than six stator modules 40.That is, electric machine 10 of FIG. 1 may operate with one, two, three,four, five, six, or seven stator modules 40. In addition, the statormodules used may be arranged symmetrically or asymmetrically. Forexample, if two stator modules are used, stator modules 40 a and 40 bmay be used to form an asymmetrical version of electric machine 10.Alternatively, modules 40 a and 40 d may be used to form a symmetricalversion of electric machine 10.

In electric machine 10, each stator module 40 includes a stator modulehousing 42 and at least one stator segment 44 housed within statormodule housing 42. Preferably, each stator segment 44 is identical toall of the other stator segments of electric machine 10. In thearrangement of FIG. 1, electric machine 10 is provided as a three-phaseelectric machine, and each stator module 40 includes six stator segments44 that are designated by reference numerals 44 a, 44 b, 44 c, 44 d, 44e and 44 f respectively in FIG. 1 for descriptive purpose. As will bedescribed in more detail below, the positioning of the six statorsegments 44 a-f within stator module housing 42 in combination with thepositioning of each stator module within stator assembly 14 determineswith which phase of the electric machine the stator segment isassociated.

As best illustrated in FIG. 3, each stator segment includes a core 46and coils 48 with core 46 being a U-shaped magnetic core having coils 48around each leg of core 46. In this example, each stator segment 44 mayalso include a core bracelet 50 attached to the sides of the U-shapedcore at the ends of the legs of the U-shaped core. Core bracelets 50 maybe configured to fully surround the ends of U-shaped core 46 to providean enlarged stator pole face 51 at each end of core 46. The use of corebracelet 50 also allows the ends of core 46 to extent through corebracelets 50 so that the ends of core 46 make up at least portions ofstator pole face 51.

Core bracelets 50 may be formed from thin film soft magnetic material,powdered metal, or any other desired magnetic material. In someexamples, core bracelets are formed from magnetically permeable metalpowder that is pressed into the desired shape. As illustrated best inFIG. 3, core bracelets 50 may have a uniform thickness perpendicular tostator pole face 51. This use of a uniform thickness allows corebracelet 50 to be easily and economically pressed from a powdered metalmaterial.

When electric machine 10 is operating in a motor mode, stator segments44 of each stator module 40 may be selectively energizable by thecontroller 18 through bus bar module 16. When electric machine 10 isoperating in a generator mode, energy may be generated by theelectromagnetic interaction between rotor assembly 12 and stator modules40, and transferred to power source 26 through bus bar module 16. Tothis end, bus bar module 16 may be in electrical communication withcoils 48 of each of stator segments 44 a-f through associated electricalleads 52. Electrical leads 52 may be integrated within stator modules40, as discussed in further detail below. Bus bar module 16 may also bein electrical communication with controller 18 through electricalconductors 54, each of which corresponds to a phase of electric machine10. Bus bar 16 may also be used to connect each electrical conductor 54,which is associated with a phase of electric machine 10, to each of theappropriate electrical leads 52 in stator modules 40 as described indetail in the referenced PCT patent applications PCT/US2010/048027, andPCT/US2010/048028.

Referring now to FIGS. 4 and 5, the specific configuration of anexemplar magnetic core 46 for the particular examples shown in FIGS. 1-3will be described in more detail. In these examples, each individualone-piece magnetic core 46 is formed by winding a continuous ribbon ofthin film soft magnetic material into a desired shape. In this example,the shape is a generally oval shape as indicated by winding 55 in FIG.4. Magnetic cores that are formed using this process of forming amagnetic core by winding many layers of thin film soft magnetic materialto form a bulk core is generally referred to as tape wound magneticcores.

Since thin film soft magnetic materials such as amorphous metal ornano-crystalline materials are typically provided in very thin tape orribbon form (for example, a few thousandths of an inch or mil thick oreven less than 1 mil thick), winding 55 may be made up of hundreds ofwinds or layers of material as illustrated by lines 56 in FIGS. 4 and 5.Once wound into the desired shape, winding 55 may be annealed to removeany stresses that may have been caused by the winding process. Thenwinding 55 may be saturated with an adhesive material such as a verythin wicking epoxy that may be heat cured to bind winding 55 into arigid piece.

Once annealed, thin film soft magnetic materials may be very hard andvery brittle making them somewhat difficult to machine. In the exampleshown in FIGS. 4 and 5, winding 55 requires only one cut in order to cutwinding 55 into two U-shaped pieces. Each U-shaped piece may provide oneof magnetic cores 46. As illustrated in FIG. 5, each of the two U-shapedpieces that result from cutting winding 55 are made up of a plurality ofconcentric U-shaped layers 57 of thin film soft magnetic material.

In some implementations, core 46 may be made from a nano-crystalline,thin film soft magnetic material. In other implementations, any thinfilm soft magnetic material may be used, and can include, but are notlimited to, materials generally referred to as silicon iron, amorphousmetals, materials similar in elemental alloy composition to amorphousmetal materials that have been processed in some manner to furtherreduce the size of the crystalline structure of the material, and anyother thin film materials.

Although the thin film soft magnetic material making up cores 46 hasbeen primarily described as amorphous metal or nano-crystallinematerial, the present disclosure is not limited to these specificmaterials. Instead, any magnetic material that can be provided as a thincontinuous tape or ribbon may be used to provide a tape wound magneticcore as described herein.

One advantage to this configuration is that when assembled into anelectromagnetic assembly as described above, each one-piece magneticcore provides the entire return path for the two stator poles formed bythe legs of the U-shaped magnetic core. This eliminates the need for aback iron to magnetically interconnect all of the stator poles.

Another advantage of the above described configuration is that there areno parasitic gaps within the magnetic cores. That is, each layer of thinfilm soft magnetic material extends continuously from one end or pole ofthe U-shaped magnetic core all the way around to the opposite end orpole of the U-shaped magnetic core. Therefore, this configurationorients each of the layers of thin film soft magnetic material in theproper orientation for directing magnetic flux through the magnetic corealong the length of each layer of thin film soft magnetic material asillustrated by arrow 58 in FIG. 5.

As described above, each stator segment 44 within each stator module ispreferably identical to all of the other stator segments in all of theother stator modules of the electric machine. This modular configurationprovides several advantages over conventional electric machines.

First, by using a certain stator segment design for all of the statorsegments of a particular electric machine, the magnet core and thewindings that are used for the stator segment may be economicallyproduced in mass quantities. In the case of a magnetic core that isformed from thin film soft magnetic material, this can be advantageous,because of the difficulties associated with manufacturing magnetic coresusing these types of materials. Electric motors that use magnetic coresformed from thin film soft magnetic material may provide significantadvantages over conventional iron core electric motors because thin filmsoft magnetic material can operate at very high frequencies withoutincurring high core losses. However, the difficulties associated withmanufacturing magnetic cores for electric motors using these low lossmaterials have previously prevented these materials from becomingcommercially successful in electric motors.

In addition to using the same magnetic core design for all of the statorsegments of a particular electric machine, the same magnetic core designmay be used for an entire family of electric machines. This may beaccomplished by providing a variety of configurations of windings and avariety of stator module housings and other components that areassociated with the same magnetic core design. Each electric machineassociated with the family of machines would then use the one magneticcore design along with a particular winding configuration and aparticular stator module housing. This may further increase theeconomies of scale associated with producing the particular magneticcore and associated family of electric machines.

In another advantage of the modular design described above, the sameelectric machine design may be used to provide a variety of electricmachines with different power outputs. For example, in the case in whichthe electric machine is used as a hub motor for an electric scooterapplication, the same basic motor design may be used to provide anentry-level scooter with modest power output, a mid-level scooter withmoderate power output, and a high-end scooter with high power output. Ina specific example of this approach, an electric hub motor for a scootermay be designed to include space for up to six stator modules. Anentry-level scooter may be provided with two stator modules included inthe motor, a mid-level scooter may be provided with four stator modulesincluded in the motor, and a high-end scooter may be provided with sixstator modules included in the motor. This approach enables the samebasic motor design to be used for all three power levels of scooter,which significantly reduces the costs associated with both developingthe scooter design and manufacturing the scooter. This approach alsoprovides the unique ability to upgrade the motor to a higher performancemotor later, by adding one or more stator modules.

Most conventional electric motors are designed to operate at 50 to 60 Hzbecause these are the frequencies available on conventional ACelectrical power grids. One of the reasons AC power is typicallyprovided at these frequencies is that these frequencies are well withinthe frequency capabilities of a conventional iron core motor. Even inthe case of specialty iron core motors, the frequencies typically remainbelow 400 Hz. This is because conventional iron core materials cannotrespond to the changing magnetic fields any more quickly than thiswithout causing very large losses that show up in the form of heat.

As described above, the electric machine designed in accordance with thedisclosure may use low loss thin film soft magnetic material to form themagnetic cores of the stator segments. Low loss magnetic materials suchas amorphous metal and nano-crystalline magnetic materials are typicallyprovided as a thin continuous ribbon or tape. The methods andarrangements disclosed herein provide cost effective methods ofproducing electric motors and/or generators using these low lossmaterials. The use of low loss thin film soft magnetic material for thecore material of an electric machine allows for operation at very highfrequencies while maintaining high efficiency. These frequencies may besubstantially greater than 400 Hz while still providing extremely highefficiencies and may be operated at frequencies as high as or greaterthan 2500 Hz.

As described above, exemplar electric machine 10 includes fifty-sixpairs of permanent magnets evenly spaced around rotor assembly 12 andeach stator module 40 includes six stator segments 44. In the exampleshown in FIG. 1, the stator segments 44 within a given stator module 40are arranged with a particular stator segment spacing 60 betweenadjacent stator segments 44. In this example, electric machine 10 isconfigured to have a rotor pole to stator pole ratio of four to three.That is, four pairs of permanent magnets fit within a given arc 62 ofelectric machine 10 and three adjacent stator segments 44 of a givenstator module fit within arc 62. Although electric machine 10 will bedescribed as using a rotor pole to stator pole ratio of four to threefor descriptive purposes, this is not a requirement. Instead, anydesired ratio between the number of rotor poles relative to stator polesmay be used and still remain within the scope of the disclosure.

Arc 62 corresponds to one fourteenth of the diameter of electric machine10 since four evenly spaced permanent magnets fit within arc 62 andelectric machine includes a total of fifty-six permanent magnets 32evenly spaced around rotor assembly 12. This means that there is spacefor a total of forty-two stator segments 44 around stator assembly 14 ifstator assembly 14 is fully populated with stator segments evenly spacedat stator segment spacing 60. Therefore, an electric machine of thisconfiguration with a full complement of forty-two stator segments 44 mayhave seven stator modules that each include six evenly spaced statorsegments 44 as illustrated by electric machine 64 in FIG. 6.

As described above, electric machines in accordance with aspects of thedisclosure may use less than a full complement of stator modules.Additionally, specific stator module designs and electric machinedesigns may make it difficult to maintain a constant stator segmentspacing between the stator segments at the ends of adjacent statormodules. For example, the thicknesses of the stator module housings oftwo adjacent stator modules may be such that it is not possible tomaintain a constant stator segment spacing between the stator segmentsat the ends of the adjacent stator modules. Therefore, specific electricmachine and stator module designs, or the use of less than a fullcomplement of stator modules within a particular electric machinedesign, may create a stator pole gap larger than the stator segmentspacing between adjacent stator segments within the associated statormodules. This larger stator pole gap can lead to imbalances in themagnetic flux associated with the stator segments adjacent to the largerstator pole gap relative to the other stator segments in a statormodule. These imbalances can cause inefficiencies in the operation ofthe electric machine.

Referring back to FIG. 1, electric machine 10 includes only six evenlyspaced stator modules 40 with each stator module including only sixstator segments 44. This results in a total of thirty-six statorsegments within stator assembly 14 even though forty-two stator segmentswould fit in electric machine 10 if a full complement of stator segmentswere used with constant stator segment spacing 60. In other words, sixof the potential forty-two stator segments are omitted in electricmachine 10. This use of fewer than a full complement of stator segments44 within stator assembly 14 results in a stator pole gap 66 between thestator segments at the ends of adjacent stator modules. This stator polegap 66 is larger than the stator segment spacing 60 between adjacentstator segments within stator modules 40. In electric machine 10, statorpole gap 66 is twice the size of stator segment spacing 60 because sixpotential stator segments are omitted and the six stator modules arespaced equally around stator assembly 14. This larger stator pole gap 66between the stator segments at the ends of adjacent stator modules mayalso cause a phase shift with regard to the relative positioning of thestator segments within adjacent stator modules. As mentioned above, busbar 16 may be used to correct for this phase shifting as described indetail in the referenced PCT patent applications PCT/US2010/048027, andPCT/US2010/048028.

As mentioned above, the presence of larger stator pole gap 66 may causeimbalances in the magnetic flux associated with the energizing of thestator segments adjacent to the larger stator pole gap. These imbalancescan lead to inefficiencies in the operation of the electric machine. Inorder to avoid these potential imbalances and in accordance with aspectsof the disclosure, electric machine 10 may further include terminationcores 68 that are spaced apart from adjacent stator segments 44 bystator segment spacing 60.

Termination cores 68 may be similar in construction to cores 46 ofstator segments 44. In this example, termination cores 68 are U-shapedcores formed from a low loss thin film soft magnetic material such asamorphous metal or nano-crystalline material in a manner similar to thatdescribed above for cores 46. As illustrated in FIG. 7, terminationcores 68 may also include core bracelets 50 for enlarging the statorpole faces associated with termination cores 68.

In this example configuration, termination cores 68 are not activeelectromagnetic assemblies like stator segments 44. Instead, they may bepassive magnetic cores that do not include coils for electromagneticallyenergizing termination core 68. Furthermore, termination cores 68 may beattached to, or included within, an associated stator module.Additionally, terminal cores may be provided at one or both ends of anassociated stator module. Alternatively, termination cores 68 may beprovide as separate components relative to the stator modules.

In accordance with aspects of the disclosure, termination cores 68provide an additional magnetic flux return path for magnetic fluxgenerated by energizing an adjacent stator segment 44. This additionalflux path helps balance the magnetic flux associated with the energizingof an adjacent stator segment and virtually eliminates the negativeeffects associated with having a stator pole gap larger than the statorsegment spacing. Therefore, the use of termination cores 68 allow for awide variety of stator module configurations to be used in a givenelectric machine design without creating the negative effects associatedwith a stator pole gap that is larger than the stator segment spacing.

As illustrated best in FIG. 7, since termination cores 68 do not includecoils, termination cores 68 may have shorter legs compared to cores 46of stator segments 44. This allows termination cores 68 to be somewhatshorter than stator segments 44. This, along with the fact thattermination cores 46 do not include coils, means that termination cores68 can provide additional space that may be needed for other componentsin smaller diameter electric machine designs. For example, the statormodule housings of adjacent stator modules may require enough space thatthe associated stator modules are not able to be placed close enoughtogether to maintain the desired stator segment spacing from the laststator segment in the first stator module to the first stator segment inthe next stator module. In this situation, a smaller termination coremay be placed between the stator modules with the termination core beingspaced apart from both of the stator segments and the ends of theadjacent stator modules by the stator segment spacing associated withthe electric machine. This would allow the termination core to balancethe magnetic flux associated with the energizing of both of the statorsegments at the ends of the adjacent stator modules. This configurationis illustrated in FIG. 1 in which each stator module is separated fromthe next stator module by a termination core.

As mentioned above, the use of termination cores allows for a widevariety of configurations for a given electric machine design. Forexample, an electric machine design that uses rotor arrangement 12 andstator modules 40 described above for electric machine 10 may useanywhere from one to seven stator modules. As described above forelectric machine 64 and as illustrated in FIG. 6, no termination coreswould be required if seven stator modules were used. If only one statormodule were used, a termination core may be used at both ends of thestator module and the entire remainder of the stator assembly would bevacant. If any other number of stator modules is used, the statormodules may be grouped immediately adjacent to one another and atermination core may be placed at both ends of the grouping.Alternatively, different groupings of stator modules could be placed invarious positions around the stator assembly. In this case, terminationcores may be placed at both ends of each grouping.

Although stator modules 40 have been described as including six statorsegments and electric machine has been described as a three-phasemachine, these are not requirements. Instead, any desired number ofstator segments may be included in a stator module and the electricmachine may have any desired number of phases.

Referring now to FIGS. 1 and 8, a rotor assembly and methods of making arotor assembly in accordance with aspects of the disclosure will bedescribed in more detail. As shown best in FIG. 8, rotor assembly 12 maybe shaped very much like a conventional automotive brake drum. With thisconfiguration, rotor assembly 12 surrounds the outer perimeter of statorassembly 14. Bearings 80, or some other suitable arrangement, may beused to support rotor assembly 12 for rotation about rotational axis 30.

Rotor assembly 12 may include a back iron 82 and a rotor housing 84.Back iron 82 may be an iron alloy band having a thickness that iscapable of carrying the magnetic flux associated with permanent magnets32. Alternatively, rotor assembly 12 may be provided without including aback iron 82. In this case, rotor housing 84 may be made from a magneticmaterial and the cast rotor housing may be used as the back iron toprovide a magnetic return path for the rotor poles.

In a method of making a rotor assembly 12 in accordance with aspects ofthe disclosure, a molding arrangement 86 may be used to cast rotorhousing 84 as illustrated in FIG. 9. If a separate back iron 82 is used,back iron 82 may be supported within molding arrangement 86 and rotorhousing 84 may be cast around back iron 82. If the cast rotor housingitself is to be used for the back iron magnetic flux return path withoutthe use of a separate back iron, rotor housing 84 may be cast withoutthe use of back iron band 82. Once rotor housing 84 is formed, moldingarrangement 86 may be removed and the inner surface of rotor housing 84(onto which the rotor poles are to be formed or placed) may be machinedto precise tolerances if desired. A bearing support 88 or some otherform of supporting arrangement may also be formed and/or machined intorotor housing 84.

The use of permanent magnets for the rotor poles of the electric machinemay result in very large magnetic forces between the rotor and statorassemblies when the rotor assembly is being positioned over or aroundthe stator assembly during the assembly of the electric machine. Theselarge magnetic forces may tend to cause unwanted contact and potentialdamage to the stator and/or rotor assemblies during the assemblyprocess. Bearing support 88 may be a relatively long bearing supportthat fits over a relatively long axel on stator assembly 14. The use ofa relatively long axel and relatively long bearing support may assist inmaintaining the proper alignment between the stator assembly and therotor assembly to prevent potentially damaging contact between the rotorand stator assemblies during the assembly of the electric machine.

Once rotor housing 84 has been molded, rotor poles may be formed orplaced in rotor housing 84. In some examples, a magnet spacing track 90may be used as a jig to precisely position the permanent magnets indesired locations in the rotor housing. Magnet spacing track 90 may be aplastic strip that fits snuggly against the inside surface of rotorhousing 84. Magnet spacing track 90 may have cut outs for preciselypositioning each permanent magnet 32 within rotor housing 84. Magnetspacing track 90 may also be adhered to rotor housing 84 along with thepermanent magnets and remain part of overall rotor assembly 12.

The material used to cast rotor housing 84 may be any suitable andreadily providable casting material. Example casting materials caninclude casting materials having good thermal conductivity, goodstructural strength, and appropriate magnetic characteristics. In thecase in which the casting material of the rotor housing is used as theback iron, the casting material may be a cast iron with good magneticpermeability. Grey cast irons are an example of a suitable cast iron andthey are categorized by their mechanical strength in ASTM includingASTM-20, ASTM-25, ASTM-30, ASTM-35, ASTM-40, ASTM-50, and ASTM-60. Greycast irons with a higher mechanical strength may be used to provide alighter weight rotor housing for a given application.

In the case in which a separate back iron band 82 is used, an examplematerial is an aluminum alloy casting material. The use of aluminumalloy for the rotor housing may provide an even lighter weight rotorassembly and good thermal properties. Regardless of the casting materialused, the casting or molding process may also include forming variousfeatures into rotor housing 84 such as cooling fins, mounting points fora wheel, or any other desired features. Various additional features mayalso be machined into the rotor housing after the molding process iscomplete.

As mentioned above, electric machines in accordance with the disclosuremay take the form of a wheel hub electric machine. In this type ofapplication, the weight of the electric machine and the cost of thevarious components making up the machine are very important. Casting therotor housing as described above provides a very strong and light weightrotor assembly that is very economical when produced in relatively highvolumes. In addition, as described above for electric machine 10, thesame rotor assembly may be used for a wide variety of electric machineconfigurations by varying the number of stator modules included in theelectric machine. This potentially allows the rotor assembly to me madein even higher volumes further improving the cost effectiveness ofelectric machines designed in accordance with the disclosure.

In a radial gap electric machine such as electric machine 10 describedabove, the size of the radial gap between the rotor pole faces and thestator pole faces is very significant to the performance of the electricmachine. Maintaining a consistent radial gap for all of the stator poleswithin the electric machine is also very important for balancing themagnetic flux and ensuring the optimum performance of the electricmachine. Since electric machines in accordance with the disclosure mayinclude a plurality of independent stator modules, the precisepositioning and attaching of each of the stator modules to the statorassembly is critical. Referring now to FIGS. 10 and 11 a method ofattaching the stator modules to the stator assembly in accordance withaspects of the disclosure will be described in more detail.

FIG. 10 illustrates a stator module support arrangement 100 for use instator assembly 14 of electric machine 10 in accordance with aspects ofthe disclosure. Stator module support arrangement 100 may include arotor support arrangement 102 that is configured to allow rotor assembly12 to be attached to stator module support arrangement 100 for rotationabout rotational axis 30 of electric machine 10. Rotor supportarrangement 102 may include an arrangement for supporting bearing 80 orany other suitable arrangement for supporting rotor assembly 12 forrotation about rotational axis 30.

Stator module support arrangement 100 may also include a positionlocking surface finish 104 and mounting points 106 that are configuredto receive stator modules 40. As shown best in FIG. 11, stator modules40 may also include position locking surface finish 104. Positionlocking surface finish 104 may provide a fine scale indexing feature forassisting in holding the stator modules in the desired location as theyare being positioned on stator module support arrangement 100. Theseindexing features may be configured to allow very small incrementalmovements between stator modules 40 and stator module supportarrangement 100 while stator modules 40 are being positioned on statormodule support arrangement 100. The position locking surface finishesmay also provide an arrangement for locking stator modules 40 in placeonce they are secured to stator module support arrangement 100 usingbolts 108 or any other suitable securing arrangement. In some examples,position locking surface feature 104 may be a knurled surface finish.Alternatively, position locking surface features 104 may be a series offine scale concentric ridges, cross-hatches, or lines.

In order to precisely locate stator modules on stator module supportarrangement 100, a positioning jig 110 may be used as illustrated inFIG. 11. Positioning jig 110 may be temporarily attached to statorsupport arrangement 100 using rotor support arrangement 102. This allowspositioning jig 110 to be used to precisely locate stator modules 40 onstator support arrangement 100 relative to rotor support arrangement102. Since rotor support arrangement 102 is also used to support rotorassembly 12 once electric machine 10 is fully assembled, this approachallows positioning jig 110 to precisely locate the positions of statormodules 40 relative to the final positioning of the rotor poles orpermanent magnets 32 once electric machine 10 is fully assembled. Afterstator modules 40 have been secured in the proper positions using bolts108 or any other suitable securing arrangement, positioning jig 110 maybe removed and rotor assembly 12 may be attached to stator assembly 14.

Referring now to FIG. 12, a method 120 of making a stator module inaccordance with aspects of the disclosure will be described in moredetail with reference to stator module 40 described above. Althoughstator module 40 has been described as including six stator segments,this is not a requirement of the disclosure. Instead, the stator modulesmay include any number of stator segments and still remain within thescope of the disclosure.

Each of the stator segments 44 of stator module 40 may be assembled withstator segments 44 including tape wound core 46, two windings or coils48, and two core bracelets 50. As described above with reference toFIGS. 4 and 5, each individual one-piece magnetic core 46 may be formedby winding a continuous ribbon of thin film soft magnetic material intoa desired shape as indicate in step 122 of FIG. 12. In this example, theshape is a generally oval shape as indicated by winding 55 in FIG. 4.Once wound into the desired shape, winding 55 may be annealed to removeany stresses that may have been caused by the winding process asindicated in step 124 of method 120. Then, as indicated in step 126,winding 55 may be saturated with an adhesive material such as a verythin wicking epoxy that may be heat cured to bind winding 55 into arigid piece. Winding 55 may then be cut into two U-shaped pieces thateach may provide one of magnetic cores 46 as indicated in step 128.

Since tape wound magnetic cores 46 include legs that have a consistentcross section, the electromagnetic windings or coils 48 may be slid overeach of the legs of core 46 after coils 48 have already been formed orwound as indicated by steps 130 and 132 of method 120. This allows eachindividual coil 48 to be economically wound on a high volume and verysimple winding machine. This ability to wind coils 48 individually andprior to being installed onto cores 46 eliminates the need for the useof expensive and complicated winding machines to perform the complexwinding processes that are typically required to manufactureconventional electric machines.

In this example, round copper wire with a dielectric coating may be usedto form coils 48. However, it should be understood that any desiredelectrical conductor material and configuration may be used. Thisincludes wire formed from electrically conductive material other thancopper such as aluminum. This also includes wire stock having anydesired cross sectional shape such as square wire.

As mentioned above, core bracelets 50 may be formed from thin film softmagnetic material, powdered metal, or any other desired magneticmaterial. In some examples, core bracelets 50 are formed frommagnetically permeable metal powder that is pressed into the desiredshape as indicated in step 134. As illustrated best in FIG. 3, corebracelets 50 may have a uniform thickness perpendicular to stator poleface 51. This use of a uniform thickness allows core bracelet 50 to beeasily and economically pressed from a powdered metal material.

With coils 48 placed on core 46, core bracelets 50 may be installedaround the ends of the legs of U-shaped core 46 as indicated by step 136such that the bottom surface of core bracelet 50 is flush with thestator pole face 51 of core 46. Core bracelets 50 may be configured tofully surround the ends of U-shaped core 46 to provide an enlargedoverall stator pole face 51 at each end of core 46. Each core bracelet50 may be adhered to the sides of the end of the respective leg of core46 using any suitable adhesive material. Core bracelets 50 may also beadhered to the bottom portions of coils 48 and coils 48 may be adheredto core 46 to provide additional support to core bracelets 50 during theassembly of stator module 40.

The use of core bracelets 50 enlarges stator pole face 51 and reducesthe space between adjacent stator pole faces within stator module 40.This reduced spacing between adjacent stator pole faces improves theefficiency of an electric machine that uses this configuration byenlarging the flux linkage area of the stator poles.

As mentioned above, the use of core bracelet 50 also allows the ends ofcore 46 to extent through core bracelets 50 so that the ends of core 46make up at least portions of stator pole face 51. This allows statorpole face 51 to include all of the cut ends of each layer of the tapewound material making up core 46. By having all of the ends of thelayers of the tape wound core material extend to stator pole face 51,each layer of tape wound material provides a continuous anduninterrupted magnetic flux path from one stator pole face of theU-shaped core to the opposite stator pole face of the U-shaped core. Inother words, for the portions of the stator pole face that include thecut ends of the layers of tape wound core material, the magnetic fluxdoes not need to transition from one magnetic material to another orthrough multiple layers of magnetic material. This configurationprovides the best possible magnetic flux path between the two statorpole faces of the magnetic core for the portions of the stator pole facethat include the cut ends of the layers of tape wound core material.

In accordance with aspects of the disclosure, six assembled statorsegments 44 may be seated or supported on a temporary support 138 asindicated in step 140 of method 120. FIG. 13 illustrates an example oftemporary support 138 that includes a stator segment orienting surface142 for each stator segment 44. Each stator segment orienting surface142 is configured to precisely orient an associated stator segment 44 ina desired orientation relative to the other stator segments of thestator module that is being constructed when the stator segments arepositioned and supported against their associated stator segmentorienting surfaces as shown best in FIG. 14. Any suitable arrangementmay be used to hold stator segments 44 in place during the constructionof stator module 40 including additional supporting arrangements orclamping arrangements.

In accordance with aspects of the disclosure, temporary support 138 maybe a magnetic jig that also includes a plurality of magnets 144 locatedbelow each stator segment orienting surface 142. With thisconfiguration, magnets 144 provide a magnetic force that may hold astator segment 44 against stator segment orienting surface 142throughout the construction of a stator module 40 using method 120.Magnets 144 may be permanent magnets similar to magnets 32 used in rotorassembly 12. Alternatively, magnets 144 may be any other type of magnetincluding electromagnets that may be controlled by an external powersource.

Temporary support 138 may be formed from any suitable material that iscapable of properly supporting stator segments 44 during theconstruction of stator modules 40. In an example in which temporarysupport 138 is a magnetic jig, temporary support 138 may be machinedfrom a non-magnetic material such as an aluminum alloy.

At some point during the process of constructing stator module 40, aHi-Pot test may be performed on each stator segment 44 to insure thatthere are no shorts between the coils and the magnetic core as indicatein step 146 of method 120. This step may be done after coils 48 areinstalled on cores 46. Preferably, this test would be done before themolding steps that will be described hereinafter are performed and anystator segments that fail the Hi-Pot test would be rejected and replacedwith passing stator segments.

As indicated by step 148, method 120 may include the step of installinga wire guide arrangement 150 over the tops of stator segments 44 asillustrated in FIG. 14. Wire guide 150 may further support statorsegments 144 in their desired orientations relative to one another. Wireguide 150 may also be used to hold electrical leads 52 of coils 48 indesired positions for further assembly of stator module 40.

Method 120 may also include a step 152 of installing an electricalconnection arrangement 154 for electrically interconnecting electricalleads 52 of coils 48. As illustrated best in FIG. 14, electricalconnection arrangement 154 may be a printed circuit board (PCB) that maybe positioned over wire guide 150 and electrical leads 52 may besoldered to electrical contact points on the PCB. PCB or electricalconnection arrangement 154 may also include electrical connectors (notshown) that may be used to electrically connect stator module 40 toelectrical conductors 54 described above for electric machine 10. Asdescribed above and as illustrated in FIG. 1, electric conductors 54 maybe in electrical communication with controller 18 and may be associatedwith the various phases of electric machine 10.

With the above described configuration, different examples of the PCBmay be used to electrically interconnect electrical leads 52 of coils 48and electrical conductors 54 in a variety of different desired mannersdepending on the specific requirements for the electric machine. Forexample, in a three phase electric machine, a six stator segment statormodule would include a total of twelve coils 48 with four of these coilsbeing associated with each phase. In a relatively low voltage version ofthis type of electric machine, the PCB may be configured to electricallyinterconnect each group of four coils associated with each phase inparallel. In a relatively higher voltage version of this type ofelectric machine, the PCB may be configured to electrically interconnecteach group of four coils associated with each phase in series. In arelatively medium voltage version of this type of electric machine, thePCB may be configured to electrically interconnect each group of fourcoils associated with each phase such that there are two parallel groupsof two coils connected in series. Therefore, a plurality of differentstator module and electric machine configurations may be obtained bysimply using different PCB configurations to interconnect electricalleads 52 of coils 48 without varying any other components within statormodule 40. This provides the advantage of being able to use many of thesame components to construct a variety of electric machineconfigurations.

As indicated by step 156, a mold may be placed around stator segments 44and the other components assembled on temporary support 138 as bestillustrated in FIG. 15. In some examples, the mold may be stator modulehousing 42 that remains part of stator module 40 after method 120 iscomplete. Alternatively, the mold may be a mold that is removed afterstator module 40 is formed using method 120. A gasket 158 may be used toseal the joint between the mold and temporary support 138 and the moldmay be clamped to temporary support 138. In the case in which the moldis stator module housing 42, a termination core 68 or termination coresupport arrangement may be attached to or included as part of statormodule housing 42 if the electric machine design includes the use of atermination core associated with the stator module being constructed.

Stator module housing 42 may be made from any desired material using anydesired method. Preferably, the material used would have a high thermalconductivity to assist in the removal of heat from the stator cores andwindings as will be described in more detail hereinafter. In someexamples, stator module housing 42 may be die cast using an aluminumalloy. Alternatively, stator module housing may be machined from adesired material. If the material used to form stator module housing 42is electrically conductive, stator module housing 42 may be coated witha dielectric material. For example, in the case in which the statormodule housing is die cast from an aluminum alloy, stator module housingmay be powder coated with a dielectric material to electrically isolatestator module 42 from other components of the stator modules such ascoils 48.

As indicated in FIG. 16 and step 160 of method 120, a potting material162 may be used to fill the mold to form stator module 40 such thatpotting material 162 supports stator segments 44 in their desiredorientations. In some examples, potting material 162 is an electricallynonconductive and thermally conductive encapsulating material. Thisencapsulating material may be any suitable and readily providablematerial including, but not limited to, epoxy and filler mixtures andmixtures of pourable powders. In the case of mixtures of pourablepowders, the mixture may include a heat activated adhesive powder and afiller. The filler for either the epoxy mixture or pourable powder maybe any desired filler. Example fillers can include light weight andthermally conductive (e.g., alumina coated aluminum powder).

If an epoxy and filler mixture is used for potting material 162, theratio of the filler to epoxy may be limited by the viscosity of themixture. However, vacuum may be used to assist in filling the mold withthe encapsulating material. The use of pourable powder mixtures mayprovide the potential advantage of being able to use higherconcentrations of filler while maintaining the ability to pour thepowder mixture into the mold. The mold may be vibrated to assist in thecomplete distribution of the powder mixture throughout the mold. Oncefilled, the mold may be heated to activate the epoxy or adhesive powerthereby encapsulating and supporting the various components of thestator module within the mold.

With the above described configuration, the thermally conductive pottingmaterial 162 provides a direct thermal path from the stator segments 44to the stator module housing 42. The stator module housing 42 may thenbe in direct contact with stator module support arrangement 100 ofstator assembly 14 as described with reference to FIG. 11. When electricmachine 10 is in use, stator module support arrangement 100 may beexposed to the external environment to dissipate heat away from thestator segments 44. The exterior surface of stator module supportarrangement 100 may also be provide with fins or other heat dissipatingdevices such as a liquid cooling system if desired.

As indicated in step 164 of method 120, temporary support 138 may beremoved from stator module 40 after potting material 162 has cured.Stator module 40 may then be cleaned, inspected and tested as indicatedby step 166 to ensure stator module 40 is functioning properly. By usingmethod 120 as described above, potting material 162 may be the onlymaterial structurally supporting stator segments 44 in their desiredorientation within stator module 40 after temporary support 138 has beenremoved.

Although electric machine 10 of FIG. 1 has been described as including acontroller 18 that is configured to control all of the stator modules ofthe electric machine, this is not a requirement. Instead, each statormodule may include its own separate controller. Referring back to FIG.6, electric machine 64 may include seven stator modules 168 that aresimilar in construction to stator modules 40. However, in thisimplementation, each stator module 168 may include a PCB 170 similar tothe PCB described above with reference to FIG. 14. Each PCB 170 mayinclude a stator module controller 172 that regulates the operation ofeach stator module 168 based on an input signal 174 and a positionsignal 176. The input signal 174 can include a throttle signal, forexample, in the case where the electric machine 64 is implemented in avehicle, motorcycle, scooter, or the like. Electric machine 64 may alsoinclude a position detecting arrangement 178 for detecting the positionof stator modules 168 relative to the rotor magnets 32. Positiondetecting arrangement 178 generates position signal 176 used by thestator module controller 172 and controller 172 can regulate powerprovided to the stator module 168 from power source 26 when electricmachine 64 is operating in a motor mode. Stator modules 168 may generatepower that can be provided to, and stored in the power source 26, whenthe electric machine 64 is operating in a generator mode. Thisconfiguration eliminates the need for a bus bar as described above andonly power and the signal input and position signal need to be providedto each stator module 168.

In a three-phase version of an electric machine in accordance with thedisclosure such as electric machine 10 of FIG. 1, windings 48 of eachstator module 40 may be electrically interconnected in a conventionalwye configuration as illustrated in FIG. 17. In this example, there maybe six stator segments 44 and twelve windings 48 in each stator module40 with four windings being associated with each of the three phases;Phase A, Phase B, and Phase C. As illustrated in FIG. 17, one electriclead 52 of each of the twelve windings may be connected to a commoncenter tap 180 and these electrical interconnections may be accomplishedusing electrical conductors on PCB 154. The other electric leads 52 ofthe four windings 48 associated with each of the three different phasesmay also be interconnected with one another using electrical conductorson PCB 154. As mentioned above, controller 18 may be electricallyconnected to each grouping of windings that are associated with eachphase using the electrical conductors 54 and portions of bus bar 16associated with the respective phases. Since each stator moduleassociated with electric machine 10 may be configured in this manner,this overall arrangement for electrically connecting windings 48 ofelectric machine 10 may provide a highly parallel configuration thatresults in a relatively low voltage example of an electric machine thatmay be desirable for certain applications. Alternatively, multiplewindings associated with a given phase may be connected in series asdescribed above.

Although the arrangement of using a conventional wye configuration witha common center tap described immediately above may provide a highlyparallel, relatively low voltage electric machine, the use of a commoncenter tap 180 may allow ring currents to occur within the windingsconnected to the common center tap. If present, these ring currents maycause some efficiency losses in the electric machine.

In accordance with another aspect of the disclosure, windings 48 ofelectric machine 10 may be electrically connected in a way that helpsreduce the potential for creating ring currents. Since each winding 48is independently wound rather than being series wound like mostconventional electric machines, windings 48 may be electricallyinterconnected in a wide variety of different configurations asmentioned above. FIG. 18 illustrates one example of a configuration thatmay reduce the potential for ring currents within the interconnectedwindings of a stator module. In this example, multiple center taps 182may be provided on PCB 154 and only one lead 52 of one winding 48 fromeach phase may be connected to each center tap 182 using electricalconductors on PCB 154. The other leads 52 of each winding 48 may beelectrically interconnected with the other leads 52 of the otherwindings 48 of the same phase using electrical conductors on PCB 154.Each group of windings that are associated with each phase may beelectrically connected to controller 18 using electrical conductors 54and portions of bus bar 16 as described above.

A number of implementations of the present disclosure have beendescribed. Nevertheless, it should be understood that variousmodifications may be made without departing from the spirit and scope ofthe present disclosure. For example, although the implementationsdescribed above have described the electric machine as being a radialgap machine, this is not a requirement. FIG. 19 illustrates an axial gapelectric machine 200 designed in accordance with the disclosure.Accordingly, other implementations are within the scope of the followingclaims.

Listing of Reference Numerals 10 Electric Motor 104 Position LockingSurface Finish 12 Rotor Assembly 106 Mounting Points 14 Stator Assembly108 Bolts 16 Bus Bar Module 110 Positioning Jig 18 Controller 120 StatorModule Method 20 Input Signal 122 Winding Step 22 Position Signal 124Annealing Step 24 Position detecting 126 Binding Step Arrangement 26Power Source 128 Cutting Step 28 Radial Gap 130 Coil Winding Step 30Rotational Axis 132 Coil Installing Step 32 Permanent Magnets 134 CoreBracelet Pressing Step 40 Stator Module 136 Core Bracelet InstallingStep 42 Stator Module Housing 138 Temporary Support 44 Stator Segment140 Stator Segment Seating Step 46 Core 142 Stator Segment OrientingSurface 48 Coils 144 Magnets 50 Core Bracelet 146 Testing Step 51 StatorPole Face 148 Wire Guide Installing Step 52 Electrical Leads 150 WireGuide 54 Electrical Conductors 152 PCB Installing Step 55 Windings 154PCB 56 Lines 156 Mold Placing Step 57 U-shaped Layer 158 Gasket 58 Arrow160 Potting Step 60 Stator Segment Spacing 162 Potting Material 62 Arc164 Jig Removing Step 64 Electric Machine 166 Inspecting and TestingStep 66 Stator Pole Gap 168 Stator Modules 68 Termination Core 170 PCB80 Bearing 172 Stator Module Controller 82 Back Iron 174 Input Signal 84Rotor Housing 176 Position Signal 86 Molding Arrangement 178 PositionDetecting Arrangement 88 Bearing Support 180 Center Tap 90 MagnetSpacing Track 182 Center Tap 100 Stator Module Support 200 ElectricMachine Arrangement 102 Rotor Support Arrangement

1-75. (canceled)
 76. A electric machine having: a rotor assemblysupported for rotation about a rotational axis, the rotor assemblyincluding a plurality of rotor poles, the rotor poles being supportedfor rotation along a rotor pole circular path about the rotational axiswith a desired rotor pole spacing between adjacent rotor poles; and astator assembly comprising: a plurality of independently energizablestator segments, each stator segment including a magnetic core thatdefines a plurality of stator poles for magnetically interacting withthe rotor poles, the stator segments being positioned adjacent to therotor pole circular path such that the stator poles face the rotor polecircular path with a desired stator pole spacing between adjacent statorpoles, the stator segments also being positioned adjacent to only aportion of the rotor pole circular path such that there is at least onestator pole gap between at least two stator poles that is greater thanthe desired stator pole spacing; and a stator pole face enlarging piece,the stator pole face enlarging piece being attached to the stator poleportions of the tape wound magnetic core piece to enlarge the surfacearea of the stator pole face and allow at least portions of the ends ofat least some of the multiple layers of thin film soft magnetic tapematerial to form portions of the stator pole face. wherein the statorpole face enlarging piece fully surrounds the stator pole portions ofthe tape wound magnetic core piece and is made from a pressed powdermagnetic material with a uniform thickness perpendicular to the statorpole face, with at least one non-energizable termination magnetic corepositioned within the stator pole gap and adjacent to one of the statorsegments such that the termination core provides an additional magneticflux return path for magnetic flux associated with the energizing of theadjacent stator segment, said termination core not including coils andnot being an active electromagnetic assembly being shorter than anadjacent stator segment.
 77. The electric machine of claim 76 whereinthe stator assembly includes a plurality of independent stator moduleswith each stator module including a plurality of the stator segments, atleast one of the independent stator modules including at least onetermination magnetic core.
 78. The electric machine of claim 77 whereinthere is a stator pole gap between each stator module and wherein eachstator module includes at least one termination core.
 79. The electricmachine of claim 76 wherein the magnetic cores of the stator segmentsare U-shaped magnetic tape wound cores having two legs and formed frommultiple layers of thin film soft magnetic tape material having adesired tape width and tape thickness, the two legs of each U-shapedmagnetic tape wound core defining two stator poles of the associatedstator segment.
 80. The electric machine of claim 76 wherein thetermination magnetic cores are U-shaped magnetic tape wound cores formedfrom multiple layers of thin film soft magnetic tape material having adesired tape width and tape thickness.
 81. The electric machine of claim79 wherein: the rotating electric machine is a radial gap electricmachine; each stator segment is positioned such that the two statorpoles of each stator segment are located adjacent to one another and inline with one another along a line that is parallel with the rotationalaxis of the electric machine; and the rotor poles are pairs of rotorpoles formed from adjacent pairs of permanent magnet segments configuredto form rotor poles of opposite magnetic polarity, each pair ofpermanent magnet segments being positioned such that the two permanentmagnet segments are located adjacent to one another and in line with oneanother along a line that is parallel with the rotational axis of theelectric machine such that the two permanent magnet segments define twoadjacent circular paths around the rotational axis of the electricmachine when the rotor is rotated about the rotational axis of theelectric machine, each of the two adjacent circular paths facing anassociated one of the stator poles of each independently energizablestator segment.
 82. A magnetic core for use in a stator assembly of anelectric machine having a rotor with a plurality of rotor poles, themagnetic core comprising: a tape wound magnetic core piece formed frommultiple layers of thin film soft magnetic tape material of a desiredtape width and tape thickness, the tape wound magnetic core piecedefining at least portions of a plurality of stator poles adapted tomagnetically interacting with the rotor poles of the electric machine,each stator pole having a pole face adapted to face the rotor of theelectric machine, each stator pole face including at least portions ofthe ends of at least some of the multiple layers of thin film softmagnetic tape material; and a stator pole face enlarging piece, thestator pole face enlarging piece being attached to the stator poleportions of the tape wound magnetic core piece to enlarge the surfacearea of the stator pole face and allow at least portions of the ends ofat least some of the multiple layers of thin film soft magnetic tapematerial to form portions of the stator pole face; wherein the statorpole face enlarging piece fully surrounds the stator pole portions ofthe tape wound magnetic core piece and is made from a pressed powdermagnetic material with a uniform thickness perpendicular to the statorpole face, with at least one non-energizable termination magnetic corepositioned within the stator assembly and adjacent to a stator segmentsuch that the termination core provides an additional magnetic fluxreturn path for magnetic flux associated with the energizing of theadjacent stator segment said termination core not including coils andnot being an active electromagnetic assembly.
 83. The magnetic core ofclaim 82 wherein the tape wound magnetic core piece is a U-shapedmagnetic core piece formed by winding multiple layers of the thin filmsoft magnetic tape material into an oval shape and cutting the windingto form two U-shaped magnetic core pieces, each U-shaped magnetic corepiece defining at least portions of two stator poles.
 84. The magneticcore of claim 83 wherein the stator pole face includes the cut ends ofeach layer of the thin film soft magnetic tape material.